The optical response of nanostructured surfaces and the composite diffracted evanescent wave model

Investigations of the optical response of subwavelength-structure arrays milled into thin metal films have revealed surprising phenomena, including reports of unexpectedly high transmission of light. Many studies have interpreted the optical coupling to the surface in terms of the resonant excitation of surface plasmon polaritons (SPPs), but other approaches involving composite diffraction of surface evanescent waves (CDEW) have also been proposed. Here we present a series of measurements on very simple one-dimensional subwavelength structures to test the key properties of the surface waves, and compare them to the CDEW and SPP models. We find that the optical response of the silver metal surface proceeds in two steps: a diffractive perturbation in the immediate vicinity (2–3 mu m) of the structure, followed by excitation of a persistent surface wave that propagates over tens of micrometres. The measured wavelength and phase of this persistent wave are significantly shifted from those expected for resonance excitation of a conventional SPP on a pure silver surface.

Dynamics of an axisymmetric electromagnetic 'crucible' melting

Different industrial induction melting processes involve free surface and melt-solid interface of the liquid metal subject to dynamic change during the technological operation. Simulation of the liquid metal dynamics requires to solve the non-linear, coupled hydrodynamic-electromagnetic-heat transfer problem accounting for the time development of the liquid metal free boundary with a suitable turbulent viscosity model. The present paper describes a numerical solution method applicable for various axisymmetric induction melting processes, such as, crucible with free top surface, levitation, semi-levitation, cold crucible and similar melting techniques. The presented results in the cases of semi-levitation and crucible with free top surface meltings demonstrate oscillating transient behaviour of the free metal surface indicating the presence of gravity-inertial-electromagnetic waves which are coupled to the internal fluid flow generated by both the rotational and potential parts of the electromagnetic force.

Cimentos convencionais e adesivos na cimentação final em prótese fixa

Os cimentos dentários na função de preencher a interface entre a superfície dentária e superfície interna da prótese nos coloca frente a uma diversidade de substratos e técnicas. O presente trabalho visou rever conceitos associados aos cimentos dentários, a evolução destes materiais junto aos diferentes sistemas cerâmicos e suas limitações no seu universo bem como a estratégia da sua aplicação em superfícies resistentes ou não ao ácido condicionante. Para alcançar a resposta de qual o melhor método na escolha de um material para cimentação de próteses fixas, este trabalho também apresenta uma comparação entre os cimentos dentários convencionais e resinosos. Este trabalho consiste numa revisão bibliográfica de forma a pesquisar de forma geral os cimentos de uso na medicina dentária. Foi realizada uma pesquisa, em abril de 2016, nas bases de dados da PubMed e B-on e em obras de caráter científico com o intuito de recolher informações sobre o assunto em um intervalo temporal de 10 anos. Os critérios escolhidos foram casos clínicos, revisão de literatura e estudos in vitro, segundo o seu rigor científico e interesse para o tema. O resultado sobre os testes de resistência utilizados nos estudos, os testes de aderência do cimento ao dente podem variar amplamente. O tratamento de superfícies e a evolução tecnológica podem ser eficazes na escolha desses materiais, bem como a comparação dos tipos de falhas que ocorrem na interface adesivas. A conclusão que se obteve é que os materiais raramente são comparados com um padrão e muitas vezes as condições experimentais variam.

Corrosion protection of PVD and paint coatings for selective solar absorber surfaces

The selective solar absorber surface is a fundamental part of a solar thermal collector, as it is responsible for the solar radiation absorption and for reduction of radiation heat losses. The surface’s optical properties, the solar absorption (á) and the emittance (å), have great impact on the solar thermal collector efficiency. In this work, two coatings types were studied: coatings obtained by physical vapor deposition (PVDs) and coatings obtained by projection with different paints (PCs) on aluminum substrates. The most common industrial high performing solar selective absorbers are nowadays produced by vacuum deposition methods, showing some disadvantages, such as lower durability, lower resistance to corrosion, adhesion and scratch, higher cost and complex production techniques. Currently, spectrally selective paints are a potential alternative for absorbing surfaces in low temperature applications, with attractive features such as ease of processing, durability and commercial availability with low cost. Solar absorber surfaces were submitted to accelerated ageing tests, specified in ISO 22975-3. This standard is applicable to the evaluation of the long term behavior and service life of selective solar absorbers for solar collectors working under typical domestic hot water system conditions. The studied coatings have, in the case of PVDs solar absorptions between 0.93 and 0.96 and emittance between 0.07 and 0.10, and in the case of PCs, solar absorptions between 0.91 and 0.93 and emittance between 0.40 and 0.60. In addition to evaluating long term behavior based on artificial ageing tests, it is also important to know the degradation mechanism of different coatings that are currently in the market. Electrochemical impedance spectroscopy (EIS) allows for the assessment of mechanistic information concerning the degradation processes, providing quantitative data as output, which can easily relate to the kinetic parameters of the system. EIS measures were carried out on Gamry FAS2 Femostat coupled with a PCL4 Controller. Two electrolytes were used, 0.5 M NaCl and 0.5 M Na2SO4, and the surfaces were tested at different immersion times up to 4 weeks. The following types of specimens have been tested: Aluminium with/without surface treatment, 3 selective paint coatings (one with a poly(urethane) binder and two with silicone binders) and 2 PVD coatings. Based on the behaviour of the specimens throughout the 4 weeks of immersion, it is possible to conclude that the coating showing the best protective properties corresponds to the selective paint coating with a polyurethane resin followed by the other paint coatings, whereas both the PVD coatings do not confer any protection to the substrate, having a deleterious effect as compared to the untreated aluminium reference.

Tratamentos de superfície em rolhas de cortiça

Este trabalho foi desenvolvido na empresa Amorim & Irmãos, SA e teve dois objectivos fundamentais. O primeiro centrou-se na análise do processo de tratamento de superfície das rolhas, procurando um produto alternativo ao actualmente implementado na empresa e a sua optimização. O segundo objectivo foi a elaboração de um novo método de determinação da absorção em garrafa, que permitisse a sua determinação sem o conhecimento da massa inicial da rolha. Para a concretização do primeiro objectivo foram estudados doze produtos químicos em comparação com o actualmente utilizado, em que o objectivo foi obter-se forças de extracção entre 15 e 20 daN. Após realização do tratamento de superfície para cada produto foram realizados vários testes laboratoriais, nomeadamente: forças de extracção, vedação em tubo, absorção em garrafa, capilaridade, análise de risco à quantidade de produto adicionado e análise de risco ao tempo de distribuição do tratamento. Após análise global dos resultados obtidos verificou-se que o produto T13, embora apresente forças de extracção no limite inferior ao desejado possui uma boa estabilização. Os produtos T5 e T6 são bons alternativos ao produto actualmente implementado (T8), embora seja necessário ter alguns cuidados no seu manuseamento. O produto T5 como foi considerado mau no teste da absorção em garrafa não poderá ser utilizado para mercados mais distantes (EUA, Austrália e África do Sul) devido ao risco de ocorrência de migração de vinho através da rolha de cortiça. O produto T6 como apresentou um comportamento irregular na análise de risco à quantidade de produto adicionado, e na análise de risco à distribuição de produto, deve-se ter muita atenção à quantidade inserida no tambor assim como o tempo de distribuição. Para a concretização do segundo objectivo foi determinada a absorção em garrafa pelo método actual e comparou-se com o novo método. Apesar do desvio padrão ser de aproximadamente 0,85, pode-se afirmar que o novo método de determinação da absorção em garrafa é um método eficaz que pode ser aprovado pela empresa. Desta forma, foi possível solucionar esta questão e permitir ao laboratório de controlo de qualidade determinar a absorção em garrafa de garrafas de vinho provenientes de clientes.

Desenvolvimento de um relatório de suporte à declaração ambiental de produto: perfis de alumínio

A Avaliação do Ciclo de Vida (ACV) considera todo o ciclo de vida do produto, desde a extração e obtenção da matérias-primas, passando pela produção e fabrico de materiais e energia, até ao tratamento de fim de vida e destino final do produto. As Declarações Ambientais de Produto (DAP) são declarações ambientais Tipo III que apresentam um conjunto de informação quantificada e fidedigna, que funciona como uma excelente ferramenta de comunicação relativa ao desempenho ambiental do produto ao longo do seu ciclo de vida. Este relatório de estágio visa, por um lado, analisar os impactes ambientais no decurso do processo de produção do perfil de alumínio sujeito ao tratamento acetinado 20 natural (AC20NA) e, por outro, elaborar um relatório de suporte, que servirá de base para o desenvolvimento da DAP do perfil de alumínio AC20NA a submeter ao sistema DAPHabitat. O relatório foi elaborado tendo por base a norma EN 15804 e inclui as fases obrigatórias (A1-A3). Desta forma, utilizou-se ao software SimaPro para a análise dos impactes ambientais das várias fases do processo de fabrico do perfil de alumínio em estudo. As fases consideradas foram a extrusão, a anodização (tratamento de superfície), a Estação de Tratamento de águas Residuais Industriais (ETARI) e a embalagem. A fase que mais contribui para as diferentes categorias de impacte é a extrusão, uma vez que é nesta fase que é utilizada a matéria-prima para a produção dos perfis de aluminío.

Efeito do revestimento nas propriedades das rolhas de cortiça

A utilização de revestimentos poliméricos em rolhas de cortiça natural é uma prática recorrente na indústria de produção de rolhas. A sua aplicação tem como principal objetivo a melhoria da qualidade visual das rolhas. Contudo, este tratamento altera também as suas caraterísticas de molhabilidade, pelo que é importante otimizar os processos de revestimento de superfície. O presente trabalho teve como objetivo principal a averiguação da influência de um revestimento colorido e de diferentes tratamentos de superfície no comportamento da rolha em garrafa. Foram utilizadas amostras, cedidas pela Cork Supply Portugal, provenientes de quatro branqueamentos distintos (LVL, CSP, CPI e SIL). Foram estudadas amostras com e sem revestimento colorido e, todas elas, tratadas superficialmente com quatro tipos de tratamento (TS1, TS2, TS3 e TS4), sendo as quantidades de parafina e silicone administradas todas diferentes. Para observar o efeito do revestimento colorido e dos tratamentos de superfície nas rolhas de cortiça, procedeu-se a testes para determinação de capilaridade, inserções e forças de extração, simulando as condições de engarrafamento/extração do cliente, de forma a verificar a conformidade dos resultados. Todos estes testes procederam-se nas instalações da CSP. Foram também efetuados testes de molhabilidade pela determinação de ângulos de contacto para três diferentes solventes, nomeadamente água, formamida e diiodometano, e obtidos os Wetting Envelopes, pelo método de OWRK, de forma a prever a molhabilidade das várias amostras. Os procedimentos experimentais descritos efetuaram-se nos laboratórios da Universidade de Aveiro. Aliando as análises aos vários testes efetuados, concluiu-se que o revestimento colorido tem um possível efeito favorecedor nas propriedades mecânicas das rolhas de cortiça, possui maior recetividade aos agentes lubrificantes e maior molhabilidade. Relativamente aos tratamentos de superfície, o melhor, tendo em conta os fatores de molhabilidade, foi o TS4, proporcionando melhor vedação ao vinho. Já a respeito da lubrificação, verificou-se melhores resultados para os tratamentos TS1 e TS2. A lavação SIL apresenta menor afinidade aos agentes vedantes e a CSP possui maior recetibilidade aos agentes lubrificantes.

Estudio in vitro de la resistencia adhesiva en la interfaz de resina entre la base del pad y el resinoso utilizado en cementación indirecta de la técnica lingual

Con el fin de aminorar retrasos por descementación de cualquier accesorio durante el tratamiento de Ortodoncia Lingual, se ha considerado que la fuerza de adhesión es muy importante, especialmente cuando está ubicada en las diferentes interfaces presentes entre el bracket y la resina del PAD; entre la resina del PAD y el cemento resinoso fotopolimerizable y entre este cemento y el esmalte dental. Por lo que este estudio se ha enfocado en determinar la resistencia adhesiva en la interfaz localizada entre la resina de la base del PAD y el cemento resinoso fotopolimerizable utilizando ácido fluorhídrico y óxido de aluminio como tratamiento de superficie previo a la cementación indirecta de la técnica lingual. MATERIALES Y METODOS: El tipo de estudio fue experimental "in vitro", con una muestra de 30 cuerpos de prueba hechos con resina Transbond XT, utilizando para su confección un blíster de brackets, se siguieron tres protocolos diferentes; G1 o grupo control sin ninguna preparación, G2 con aplicación de óxido de aluminio, 50 micrones durante 10 segundos en la superficie del cuerpo de prueba, G3 con aplicación de ácido fluorhídrico al 9% en la superficie del cuerpo de prueba durante 10 minutos. Previo al test de resistencia adhesiva, se realizó los cortes de precisión en cada cuerpo de prueba, obteniendo así 45 tiras de prueba, cada una de las muestras fue adherida a un porta muestra para la prueba de micro tracción, la misma que fue realizada con la máquina universal Mini-Instron modelo 5942, a una velocidad de deformación constante de 0.5 mm/min. Los datos fueron sometidos al test de Normalidad de residuos de Shapiro Wilk (p>0,05) y de LEVENE para el análisis de homogeneidad de las varianzas. La resistencia adhesiva fue comparada entre los grupos por medio del Análisis de Varianza (ANOVA) como factor único para el procesamiento de los datos. Para todos los análisis el nivel de significancia fue del 5% (p< 0,05) con un nivel de confianza del 95% (IC95%). Se consideró estadísticamente significativo valores por debajo de 0,05. RESULTADOS Y CONCLUSIONES: El resultado del test de ANOVA, reveló que el factor de tratamiento de superficie F(2,12)=2,52;p=0,12 no es significante, por lo tanto los diferentes tratamientos de superficie (óxido de aluminio y ácido fluorhídrico) utilizados son equivalentes al grupo control, indicando que no ejercen influencia de manera significativa en los valores de Resistencia Adhesiva (RA) en la preparación de la interfaz localizada entre la resina de la base del PAD y el cemento resinoso fotopolimerizable; concluyendo que se puede utilizar cualquier protocolo de tratamiento de superficie indicado en la presente investigación.

Bitumen aggregate adhesion and bitumen rheology of hard modified binders

The waterproofing of hydraulic structure is done traiditionally like laying road on dam surface but with specific modified binders. An italian firm recently patented a new method that is re-adaptation of typical surface treatment of roads. The purpose of this study is to find out best aggregate-bitumen mixture that can perform well under service conditions of a large hydraulic structure such as dams. So, 4 different hard modified bitumen were tested with 2 aggregate types i.e. limestone and basalt. The experimental program contained the testing of bitumen aggregate adhesion, using the rolling bottle test and rheology of hard modified binders using multiple stress creep and recovery test and dynamic viscosity test. The results and discussion are presented in detail in this work.

Transition-metal 13-atom clusters assessed with solid and surface-biased functionals

First-principles density-functional theory studies have reported open structures based on the formation of double simple-cubic (DSC) arrangements for Ru(13), Rh(13), Os(13), and Ir(13), which can be considered an unexpected result as those elements crystallize in compact bulk structures such as the face-centered cubic and hexagonal close-packed lattices. In this work, we investigated with the projected augmented wave method the dependence of the lowest-energy structure on the local and semilocal exchange-correlation (xc) energy functionals employed in density-functional theory. We found that the local-density approximation (LDA) and generalized-gradient formulations with different treatment of the electronic inhomogeneities (PBE, PBEsol, and AM05) confirm the DSC configuration as the lowest-energy structure for the studied TM(13) clusters. A good agreement in the relative total energies are obtained even for structures with small energy differences, e. g., 0.10 eV. The employed xc functionals yield the same total magnetic moment for a given structure, i.e., the differences in the bond lengths do not affect the moments, which can be attributed to the atomic character of those clusters. Thus, at least for those systems, the differences among the LDA, PBE, PBEsol, and AM05 functionals are not large enough to yield qualitatively different results. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3577999]

Metal oxides prepared through the nanocasting approach-mechanistic study, surface interactions and applications in separation

Mesoporous metal oxides are nowadays widely used in various technological applications, for instance in catalysis, biomolecular separations and drug delivery. A popular technique used to synthesize mesoporous metal oxides is the nanocasting process. Mesoporous metal oxide replicas are obtained from the impregnation of a porous template with a metal oxide precursor followed by thermal treatment and removal of the template by etching in NaOH or HF solutions. In a similar manner to the traditional casting wherein the product inherits the features of the mold, the metal oxide replicas are supposed to have an inverse structure of the starting porous template. This is however not the case, as broken or deformed particles and other structural defects have all been experienced during nanocasting experiments. Although the nanocasting technique is widely used, not all the processing steps are well understood. Questions over the fidelity of replication and morphology control are yet to be adequately answered. This work therefore attempts to answer some of these questions by elucidating the nanocasting process, pin pointing the crucial steps involved and how to harness this knowledge in making wholesome replicas which are a true replication of the starting templates. The rich surface chemistry of mesoporous metal oxides is an important reason why they are widely used in applications such as catalysis, biomolecular separation, etc. At times the surface is modified or functionalized with organic species for stability or for a particular application. In this work, nanocast metal oxides (TiO2, ZrO2 and SnO2) and SiO2 were modified with amino-containing molecules using four different approaches, namely (a) covalent bonding of 3-aminopropyltriethoxysilane (APTES), (b) adsorption of 2-aminoethyl dihydrogen phosphate (AEDP), (c) surface polymerization of aziridine and (d) adsorption of poly(ethylenimine) (PEI) through electrostatic interactions. Afterwards, the hydrolytic stability of each functionalization was investigated at pH 2 and 10 by zeta potential measurements. The modifications were successful except for the AEDP approach which was unable to produce efficient amino-modification on any of the metal oxides used. The APTES, aziridine and PEI amino-modifications were fairly stable at pH 10 for all the metal oxides tested while only AZ and PEI modified-SnO2 were stable at pH 2 after 40 h. Furthermore, the functionalized metal oxides (SiO2, Mn2O3, ZrO2 and SnO2) were packed into columns for capillary liquid chromatography (CLC) and capillary electrochromatography (CEC). Among the functionalized metal oxides, aziridinefunctionalized SiO2, (SiO2-AZ) showed good chemical stability, and was the most useful packing material in both CLC and CEC. Lastly, nanocast metal oxides were synthesized for phosphopeptide enrichment which is a technique used to enrich phosphorylated proteins in biological samples prior to mass spectrometry analysis. By using the nanocasting technique to prepare the metal oxides, the surface area was controlled within a range of 42-75 m2/g thereby enabling an objective comparison of the metal oxides. The binding characteristics of these metal oxides were compared by using samples with different levels of complexity such as synthetic peptides and cell lysates. The results show that nanocast TiO2, ZrO2, Fe2O3 and In2O3 have comparable binding characteristics. Furthermore, In2O3 which is a novel material in phosphopeptide enrichment applications performed comparably with standard TiO2 which is the benchmark for such phosphopeptide enrichment procedures. The performance of the metal oxides was explained by ranking the metal oxides according to their isoelectric points and acidity. Overall, the clarification of the nanocasting process provided in this work will aid the synthesis of metal oxides with true fidelity of replication. Also, the different applications of the metal oxides based on their surface interactions and binding characteristics show the versatility of metal oxide materials. Some of these results can form the basis from which further applications and protocols can be developed.

The Surface Plasmon Resonance of Supported Noble Metal Nanoparticles: Characterization, Laser Tailoring, and SERS Application

This work deals with the optical properties of supported noble metal nanoparticles, which are dominated by the so-called Mie resonance and are strongly dependent on the particles’ morphology. For this reason, characterization and control of the dimension of these systems are desired in order to optimize their applications. Gold and silver nanoparticles have been produced on dielectric supports like quartz glass, sapphire and rutile, by the technique of vapor deposition under ultra-high vacuum conditions. During the preparation, coalescence is observed as an important mechanism of cluster growth. The particles have been studied in situ by optical transmission spectroscopy and ex situ by atomic force microscopy. It is shown that the morphology of the aggregates can be regarded as oblate spheroids. A theoretical treatment of their optical properties, based on the quasistatic approximation, and its combination with results obtained by atomic force microscopy give a detailed characterization of the nanoparticles. This method has been compared with transmission electron microscopy and the results are in excellent agreement. Tailoring of the clusters’ dimensions by irradiation with nanosecond-pulsed laser light has been investigated. Selected particles are heated within the ensemble by excitation of the Mie resonance under irradiation with a tunable laser source. Laser-induced coalescence prevents strongly tailoring of the particle size. Nevertheless, control of the particle shape is possible. Laser-tailored ensembles have been tested as substrates for surface-enhanced Raman spectroscopy (SERS), leading to an improvement of the results. Moreover, they constitute reproducible, robust and tunable SERS-substrates with a high potential for specific applications, in the present case focused on environmental protection. Thereby, these SERS-substrates are ideally suited for routine measurements.

Surface science studies of strong metal-oxide interactions on model catalysts

The strong metal support interaction (SMSI) was first described in 1978 by Tauster [1-4]. The effect was observed as a severely negative effect on CO and H2 uptake on the catalyst after high temperature calcination under reducing conditions (heating above ~ 700 K) [1,2]. It also had a negative effect on the reaction rate for reactions, such as alkane hydrogenolysis [5,6]. It appeared that the effect occurred for catalysts comprised of reducible supports which were treated at elevated temperature in reducing conditions [2-4]. A classic support which has manifested this behaviour in many studies is TiO2. Over the years following the first discovery of SMSI it has been recognised that the effect is not always negative – for instance for the CO-H2 reaction for which it appears to have a positive effect [5,6]. Further it was noted that hydrogen reduction was not necessary to observe the effect of CO adsorption suppression, it also occurs by vacuum treatment [7], though it should be noted that vacuum treatment at elevated temperature is, in effect, a reducing environment.

In Vitro Adhesion of Streptococcus sanguinis to Dentine Root Surface After Treatment with Er:Yag Laser, Ultrasonic System, or Manual Curette

Objective: The purpose of this in vitro study was to evaluate the dentine root surface roughness and the adherence of Streptococcus sanguinis (ATCC 10556) after treatment with an ultrasonic system, Er:YAG laser, or manual curette. Background Data: Bacterial adhesion and formation of dental biofilm after scaling and root planing may be a challenge to the long-term stability of periodontal therapy. Materials and Methods: Forty flattened bovine roots were randomly assigned to one of the following groups: ultrasonic system (n = 10); Er:YAG laser (n = 10); manual curette (n = 10); or control untreated roots (n = 10). The mean surface roughness (Ra, mu m) of the specimens before and after exposure to each treatment was determined using a surface profilometer. In addition, S. sanguinis was grown on the treated and untreated specimens and the amounts of retained bacteria on the surfaces were measured by culture method. Results: All treatments increased the Ra; however, the roughest surface was produced by the curettes. In addition, the specimens treated with curettes showed the highest S. sanguinis adhesion. There was a significant positive correlation between roughness values and bacterial cells counts. Conclusion: S. sanguinis adhesion was the highest on the curette-treated dentine root surfaces, which also presented the greatest surface roughness.

Surface characterization of Ti-7.5Mo alloy modified by biomimetic method

Titanium and its alloys have been used in dentistry due to their excellent corrosion resistance and biocompatibility. It was shown that even a pure titanium metal and its alloys spontaneously form a bone-like apatite layer on their surfaces within a living body. The purpose of this work was to evaluate the growth of calcium phosphates at the surface of the experimental alloy Ti-7.5Mo. We produced ingots from pure titanium and molybdenum using an arc-melting furnace We then submitted these Ingots to heat treatment at 1100 degrees C for one hour, cooled the samples in water, and cold-worked the cooled material by swaging and machining. We measured the media roughness (Ra) with a roughness meter (1.3 and 2.6 mu m) and cut discs (13 mm in diameter and 4 mm in thickness) from each sample group. The samples were treated by biomimetic methods for 7 or 14 days to form an apatite coating on the surface. We then characterized the surfaces with an optical profilometer, a scanning electron microscope and contact angle measurements. The results of this study indicate that apatite can form on the surface of a Ti-7.5Mo alloy, and that a more complete apatite layer formed on the Ra = 2 6 mu m material. This Increased apatite formation resulted in a lower contact angle (C) 2010 Elsevier B.V. All rights reserved